Ok and they use KVM instead of Xen with virtio drivers.
Paper about their systems: http://blog.bytemark.co.uk/wp-content/uploads/2012/12/Design...
What I'm interested in though is KVM now generally considered better than Xen? When I last looked into it a few years ago, there wasn't much in it and KVM had some key disadvantages. Is KVM now distinctly better than Xen as I'm admittedly inferring from your comparison?
Xen and KVM both drew from the same code, i.e. qemu, but qemu now has all the important patches from KVM, and has featured paravirtualised I/O for years.
So I don't think the choice or virtualiser is fundamental to how you build a hosting platform any more - we could have built BigV on top of Hyper-V if we were masochistic enough ;-) and it would look the same from the outside.
One main difference between our platforms is that our storage is decoupled (but not very far) from the CPU, so you can attach up to 8 discs of different grades to your virtual machine. We can also live-migrate running machines, and running discs to keep things running, rather than just carving up individual boxes, discs & all, in our old VPS model.
Bytemark do indeed have more granular server specs, but Brightbox have snapshots, load balancing, distributed firewall, cloud ips, multiple zones (in geographically separate datacenters), ec2 compatibility.
Flexibility means different things to different users.
Can either offer a service where you can create a new server setup with a RoR / Db setup from an image though?
I mostly use Heroku until I have users these days, but I do think there's maybe a trick in offering mirroring of the heroku functionality from the cmd line :)
Keep up the great work.
You can then create new servers from that snapshot as required.